81 4 DLT ENGINE LUCAS DPC FIP - FEATURES 1. EXCESS FUEL SYSTEM To assist engine starting, the excess fuel system provides at very low pump speeds the fuel delivery that is greater than the full load delivery. The system is incorporated in the delivery control mechanism, which by the action of a return spring allows the distance between the pumping plungers to be increased to a level that is more than the normal operating levels. This increased outward travel of the plungers allows an extra quantity of fuel to flow in during the filling cycle. The same is pumped out during the pumping stroke. As the Engine speed increases, the increase in transfer pressure automatically cuts-off the excess fuel. The transfer pressure pushes the delivery control system against the opposing return spring to retain it in the normal operating position. 2. TWO SPEED GOVERNOR (MINI-MAXI) l The function of the two speed governor is to control the idling. Fast idling and the maximum no-load speed of the engine. l The Governor interferes only during idling and maximum no-load conditions, to determine the position of the metering valve and thus control the fuel delivery. - During the intermediate phase, the metering valve is directly linked to the throttle lever (accelerator pedal), providing a direct control. ADVANTAGES : l Smooth response to alterations in throttle position. l Improved driveability. 3. PROGRESSIVE LOW LOAD ADVANCE (PLLA) The Low Load Advance System overrides the normal speed advance system. Under low load conditions, due to reduced fuel supply, there is a tendency for the timing to retard. The low load advance system compensates for this characteristic by slightly advancing the injection at reduced fuel levels. The type of low load advance system used on Tata Safari is called the progressive low load advance (PLLA) system. The advantage of the PLLA system is, that it progressively changes the advance to suit the engine load conditions. Thus helps in achieving better emissions and also reduces transient noise. 4. SUPPORTED TOOTHED BELT TYPE DRIVE l The assembly consists of drive shaft assembly supported by two bearings and in the pump housing the shaft is connected to the pump hydraulic head by an intermediate shaft. l The bearing opposes the loading created by the drive belt, thus maintaining the alignment of the drive shaft and the hydraulic head. ADVANTAGES : l Smoother Running l Pumping drive draws lesser power from the engine l Noise reduction 5. BOOST CONTROLLER (Fig 165) The Boost Controller is necessary on the FIP fitted to turbo charged applications, in order to adjust the maximum fuel delivery in accordance with the variations in the boost pressure from the turbo charger. The fuel adjustment plate and the roller shoes on these pump are provided with ramps to allow for the progressive change in fuel delivery as the assembly move axially on the rotor by the action of the actuating piston moving against a carriage return spring. The boost controller consists of a piston valve moving within a valve body. The valve is linked to a pair of Fig. 165 Backleak return Boost pressure inlet Piston Discharge to transfer pump inlet Valve body Fuel adjusting screw Spring Spacer Diaphragms
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